Amplifying device for use in wireless telegraphy



J. B. BOLITHEO.

AMPLIFYING DEVICE FOR USE IN WIRELESS TELEGRAPHY.

APPLICATION FILED SEPT. 18, 1920.

Patented Feb. 21, 1922.

+ lll---- --1||f r 7 T 1 1 Z J 8 A J I /8 11 ll l ljlb UNITED STATES JOHN B. BoLrrrio, or ELTHAM, ENGLAND.

AMPLIFYING- DEVICE FOR USE IN To all whom it may concern:

Be it known that, 1, JOHN BRUCE BOLITHO, a subject of the King of GreatBritain, and residing at Eltham, in the county of Kent, England, have invented certain new and useful Improvements in Amplifying Devices for Use in Wireless Telegraphy, of which the following is a specification.

This invention relates to amplifying arrangements used in wireless. telegraphy. Such amplifying arran ements are also a plicable for use as 're ays. The princip e on which the invention is based will be understood from the accompanying diagram.

Let us assume that the plate 1 of a threeelectrode valve is connected in a circuit containing reactance 4, a high voltage battery 6, an indicating or recording device or relay 7, and say a -milli-ammeter 8 to the filament 3; 6, 7 and 8 are shunted by a capacity 5 of suitable size in order to provide a low resistance path for oscillating currents. The grid 2 is connected through a tuned reactance 9 (coupled in the normal way with react nce 4 in the plate circuit), a suitable num er of cells 10 and a potentiometer 11- to the filament 3. These cells 10 land the potentiometer 11 are used to control the potential of the grid 2 relatively to the filament 3. If these cells were removed the circuit would start oscillating and would maintain oscillations on its own account, but if the negative potential on the grid '2 were increased it would be found that there was a point at which the circuit would not sustain and amplify very small oscillations This point is a critical one. By the present invention, the voltage is arranged so that the valve and its accompanying circuits are unable to build up and sustain any very small oscillations.

Now let us suppose that the potential of thegrid is arranged to he say 0.1 volt less than the critical point referred to above, at which the valve may be said to be unable to initiate oscillations. Then, if incoming signals are applied to the grid circuit so that the potential of the grid of the valve is caused to oscillate, when the oscillations cause the grid to be raised to a potential of the critical value or greater, oscillations will build u rapidly in the anode and grid circuits, and will be sustained until quenched by some external a ency. As soon as the valve starts to oscfilate, due to impulses received for instance from coil 33 in a signal WIRELESS TELEGRAPHY.

v Specification of Letters Patent. Patented Feb, 21, 1922, Application filed September 18, 1920. Serial No. 411,104.

circuit inductively coupled with coil 9, the anode current between 3. and 1 becomes very much greater than before, thus giving the requlred amplification. The use' of this principle combined with a method of rapid quenching is the basis of the present invenwithout arrangements to apply a differentpotential to the second as compared with the first. In the arrangement shown, grid 2, of the first valve is connected to grid 13 of the quenching valve through lead 18, and a variable battery 19 in parallel with a shunt capacity 20. The plate 12 of. the second va ve is joined to its filament 14 through lead 21, a reactance 22 and. a source of alternating current 23 of a frequency which will generally be much less than that of the incoming signal. The reactance coil 22 in this plate circuit, which we may term the quenching circuit, is coupled to the coil 9 connected to the grid 2 of the amplifying circuit, but with its reactance reversed. Other details indicated in the diagram of connections of the two valves are a tuning condenser 34 in parallel with coil 9, a shunt capacity 35 in parallel with battery 10, a voltmeter'36 between'battery 10 and the filament-3, and a milli-ammeter 37 in the circuit of thehigh tension supply 23 leading to filament 14.

Now it will be seen that when the potential of the late 12 of the quenching circuit becomes su ciently positive, the reactances of the two plate circuits will balance out as the reactance f coil 22 is reversed, i. e. tending to damp out oscillations, so that the oscillations in circuit 9, 34, will be quenched.

Again, if the plate 12 of the quenching circult is brought to a higher positive potential, the resultant of the two reactances will be a reversed reactance, and the oscillations will be quenched even more rapidly. When the potential of the plate 12 of the quenching circuit is negative, the quenching circuit becomes inoperative and the amplifying circuit I is able to be trigged (set in oscillation and the oscillations will persist with muc increased anode current until the resultant reactance again becomes small enough or strongly enough reversed to damp out the oscillations. It will be seen that the reactance of the amplifying circuit is varied according to the modulations which are imposed for quenching purposes. The action really amounts to varying intermittently the oscillation resistance by electrical means, with the use of a valve, which serves to damp out periodically the oscillations produced by a trigged valve.

The source of high tension A. C. supply 23, is shown as consisting of a coil 24: connected across the terminals of a capacity 25 between coil 22, and filament 14 in the quenching circuit, while coil 24 is coupled inductively with coils 26, 27, in a valve circuit for generating oscillations. 0f the coils, 26 is connected between the grid 30 andcathode 31 ot the valve, whose plate 29 is connected to the terminal of a high voltage supply 32, while coil 27 is connected in parallel with capacity 28 between filament 31 and "the terminal of the high voltage supply 32, In place of the arrangement last above described, any source of electrical oscillations or impulses may be used which will make the plate 12 intermittently and sufficiently positive to bring the reversed reactance between the coils 9 and 92 into operation, so as to produce a quenching action,

The signals may be applied to the valve circuit in any suitable manner, so that when signals are received the valve will be trigged owing to the slight changes in voltage on the grid 9;.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to bcper- "formed, ll declare that what if claim is 1. An amplifying arrangement for use in wireless telegraphy, wherein automatic electrical means are employed for damping out periodically the oscillations produced in a circuit by a itrigged amplifying valve, such automatic electrical means of damping comprising a valvevarying intermittently the oscillation resistance of the circuit of the trigged amplifying valve.

2' An amplifying arrangement for use in wireless telegraphy comprising a plurality of three electrode valves, a reactance in the plate and filament circuit of each of said valves, said reactances being coupled together but acting'in opposite directions, the filaments and grids of the said valves being connected together in parallel respectively, a reactance in the grid circuits, a receiving circuit with a reactance, all the said react- :ances being coupled together and means for supplying a high tension alternating current to the plate and filament circuit of one of the valves.

ti. An amplifying arrangement for use in wireless telegraphy comprising a plurality neonate of three electrode valves with the necessary circuits therefor, reactances in the filament and plate circuitsand in the grid circuit of said valves, said 'reactances being coupled together, a receiving circuit with a reactance coupled to the reactances of the said three electrode valves and means for suptrode valve, a reactance 111 circuit with the plate and filament circuit of said valve, a tuned ractance in circuit with the grid of said valve, means for adjusting the'potential of the grid relatively to the filament, a receiving circuit with reactance, the three reactances being coupled together, a second three electrode valve, the filament and gridof said second vale being connected in parallel with the filament and grid. of the first valve, a reactance in the plate and filament circuit of the second valve, said reactance being coupled to thereactance of the plate and filament circuit of the firstvalve but arranged in a reversed direction and means for supplying a high tension alternating current to the plate and filament circuit of the second valve. 7

5. An amplifying arrangement for use in wireless telegraphy comprising a three electrode valve, a reactance, battery and recording means in circuit with the plate and filament of said valve, a capacity in shunt with the battery and recording means, a tuned reactance in the grid circuitot said valve and coupled to the first reactance, a potentiometer for adjusting the potential of the grid-relatively to the filament, a receiving circuit with reactance, a second three electrode valve, the filament and grid of the second valve being connected in parallel to the filament and grid respectively of the first valve, a ractance in the late and filament circuit of the second va ve, said reactance acting in the opposite direction to the re= actance in the plate and filament circuit of the first valve, all said reactances bein cou pled together, and means for suppl n a high tension alternating current to the pits and filament circuit of the second valve.

6. An amplifyingarrangemcnt for use in wireless telegraphy comprising a three electrode valve, a reactance, battery and record:- ing means in circuit with the plate and filament of said valve, a capacity in shunt with the battery and recording means, a tuned reactance m the grid circuit of said valve coupled together and meansfor supplying a high tension alternating current to the plateand coupled to the first reactance, a potentiometer for adjusting the potential of the grid relatively to the filament, a receiving circuit with a reactance, a second three electrode valve, the filamentand grid of the valve, means for applying a difierent potential to the grid circuit of the second valve as compared with the grid circuit of the first valve, a reactance in the plate and filament circuit of the second valve, said reactance actin in the opposite direction to the reactance 1n the plate and filament circuit of the first valve, all said reactances being and filament circuit of the second Valve.

7.'An amplifying arrangement for use in wireless telegraphycomprising a three electrode valve, a reactance, battery and recording means in circuit with the plate and filament of. said valve, a capacity in shunt with the battery and recording means, a

tuned reactance in the grid circuit of said valve and coupled to "thefirstreactance, a potentiometer for. adjusting the potential of the grid relatively to the filament, a receiving circuit with a reactance, a second three electrode valve, the filament and grid of the second valve being connected in parallel to the filament and gridrespectively' of the first valve, a reactance in the plate and filament circuit of the-second valve, said reactance acting in the opposite direction to thereactance in the plate and filament circuit of the first valve, all said reactances being coupled together, a second reactance and capacity in parallel in the plate and filament circuit of the second valve, a third three electrode valve, means for inductively coupling the'circuit of said third three electrode valve with the second reactance in the circuit of the second three electrode valve, and means for connecting said third three electrode valve to 'a high voltage supply.

JOHN B. BOLITHO. 

